Conventionally, there has been proposed a clasp using a magnetic attraction force and a magnetic repulsion force between permanent magnets as a means for coupling end portions of an accessory such as a necklace or a bracelet and releasing the end portions; or for securing a mouth of a purse or a bag and releasing the securing. Such examples of clasps are disclosed in U.S. Patent Publication No. 2006/0096070 and U.S. Patent Publication No. 2007/0028429.
The above-described conventional clasp in the references is provided with a pair of pieces, with each having a permanent magnet incorporated therein, and both the pieces are attached to both end portions of an accessory or to a main body of a purse or a bag and its flap. Both pieces, by making opposite poles of these permanent magnets face each other, receive a magnetic attraction force to be coupled to each other. Accordingly, both the end portions of the accessory are coupled, or a mouth of the purse or the bag is secured. Further, when both the coupled pieces are rotated about an axis line of both the pieces to make the same poles of both the permanent magnets face each other, both pieces receive a magnetic repulsion force to be separated from each other. Accordingly, the coupling of both the end portions of the accessory is released, or the state of the mouth of the purse or the bag being secured is released.
However, as the permanent magnets are to be used for the clasp, a relatively high magnetic attraction force, namely a relatively strong magnetic force, is exhibited such that both pieces coupled to each other are not easily separated from each other. But, on the other hand, there is a concern that a precision instrument such as, for example, a wristwatch being one of personal belongings, is adversely affected by magnetic leakage of the strong, permanent magnets.